This invention relates in general to accumulating and transport systems and more specifically to a unit that receives and discharges integrated circuits while bringing them to a preselected temperature during their residence in the system.
In the manufacturing and use of ICs it is necessary to test them reliably and rapidly. Many ICs must be heated or cooled uniformly to a preselected temperature prior to testing to simulate actual operating conditions. Modern high-speed testing equipment must therefore include a time delay transport device that can heat or cool the IC to the preselected temperature. The transport unit must also be able to receive the ICs from "tubes" or "sticks" where they are stored in an end-to-end linear array and discharge them quickly and reliably at an input to the testing area. It is also highly desirable for the accumulation and transport system to accept any of a variety of IC packages or sizes, to have a high storage density, and to have a single input port and a single exit port to interface readily with automated feed and handling systems.
Integrated circuits usually have one of two predominant package configuration: DIP (dual-in-line packaged) and SMD (surface-mounted device). DIP ICs are generally rectangular, box-like devices of plastic or ceramic with a row of pins extending downwardly along two sides. SMD ICs, in contrast, usually have an approximately square configuration and typically have a rows of pins extending from at least two sides. In either case, during handling it is important not to permanently displace any of the pins, which can occur readily since forces as small as a few grams can introduce a permanent distortion in the position of the pin. In addition, the packages themselves can be comparatively fragile and susceptible to damage, particularly where the package material is a ceramic.
One approach to storage and transport used with DIP ICs has been to transfer the ICs from a tube into one or more holding rails that are mounted generally parallel to one another and in a circle. This assembly rotates about the common axis of rotation located at the center of the circle and inclined with respect to the ground. The ICs are loaded onto the rails at one angular position and discharged at another. The time delay and heating occurs as the rails rotate between these positions. The pins straddle the rail to hold the IC on the rail, in cooperation with other elements, as the assembly rotates. Since many SMD packaged ICs have pins on all four sides, and none project from the body of the device in a manner conductive to this "straddling", this approach has not been adapted to SMD ICs.
Another approach to the handling problem has been to feed the ICs onto a horizontal carousel. The ICs are arrayed about the periphery of the carousel. The carousel rotates each IC from a loading point to a discharge point. During this rotation, the ICs are in a heated environment that brings them up to the desired testing temperature. This approach has a low storage density.
Still another approach to handling DIP ICs is shown in U.S. Pat. No. 4,546,404 to Cedrone et al entitled "Storage Unit For An Integrated Circuit Tester". In this approach, a time-delay storage unit automatically and continuously receives, accumulates, and discharges ICs. The apparatus is organized around a frame assembly that rotates about an axis of rotation that is inclined with respect to the horizontal. The ICs slide into and out of generally parallel, elongated guideways arrayed concentrically about the axis of rotation. A drive system indexes the frame and guideways carried in the frame through a series of angular positions including a load position and an unload position. A key feature of this approach is that the DIP ICs are carried in guides that are mounted in a "ferris wheel" manner so that the ICs maintain generally the same orientation throughout the rotation.
Another handler has utilized air levitation in the storage area. The Siemens' Model 1108-HSS DIP IC handler contains an input tray having multiple fixed tracks for the incoming ICs, and a single output for the devices. Air is used to float the devices as they are moved by gravity down the fixed tracks. Two moving belts in a V configuration span the lower ends of the tracks and converge at the discharge point. This handler has a variety of limitations. It is sensitive to the geometry of the devices. It can handle reliably only devices of a configuration such as DIP ICs and certain types of SMD ICs. However, even with these rectangular devices there is a sensitive relationship between the device and the machine. Further, since the input tracks are fixed, the tray is primarily for use with ICs of only one size. Yet another significant limitation of this handler is that these multiple tracks require a like multiple number of input ports. These inputs must be fed either manually, which requires generally continuous operator attention, or the use of a complex and costly automated linear feed shuttle.
While the design considerations are different, air levitation has been used in other areas of test handlers besides storage and heat exchangers, for example in the binning channels of the Daymarc Model 1157 test handler. But in each instance the tracks have been fixed in space and they have been fed with pressurized air for the levitation from a common plenum.
It is therefore an object of the present invention to provide an accumulating and transport system which accepts a variety of types and sizes of integrated circuits, particularly surface-mounted ICs.
Another object of the invention is to provide such a system which is also compact, has a high storage density, and has a single port input and a single port output.
Another object of the invention to provide an accumulating and transport system for SMDs that operates reliably, with a low incidence of jams, and which is not sensitive to package configuration or size.
Yet another object is to provide such a system which can be converted to accept ICs of a different size or package configuration easily, quickly and using a low level of skill.